Special Function: Solar Energy in Priority Function/AC Line Charging 1KW 2KW 3KW Off Grid Solar Inverter Built-in MPPT Solar SystemSolar Power Inverter Charged by AC Line by Default. When Inverter on and AC on, Battery First Charged by AC.When Switching Battery Type Selector from 7-9, as Pict Shows below, Inverter with invert from Battery despite AC Input, Using the Battery Power in Priority.When Battery Reaches Low Volt Point, Inverter will Transfer to AC Line, Charging the battery and to switch back to battery function when battery full. Using Solar Power in Priority and AC Power as Back-UP Power.